I recently re-watched both the 1934 & 1956 version(s) of The Man Who Knew Too Much back to back, both on Blu-ray. These were both excellent films.
The 1956 film is definitely the more iconic & well-known of the two, and I’m sure it made the song Que Sera, Sera extremely famous. Great song - I will admit I was somewhat unfamiliar with this prior to seeing the movie (for the first time) back in the 200X’s. I can’t imagine anyone other than Doris Day singing this 
The film’s storyline is interesting, disturbing, and compelling: I.e., a mild-mannered, law-abiding family is travelling in a foreign country - and, through no fault of their own - are caught up in international intrigue/espionage, kidnapping, etc. This just goes along with a big theme in Hitch’s films - i.e., ordinary people who are inadvertently caught up in unusual (and in many cases bizarre) situations beyond their control.
The scene when Jimmy Stewart mistakenly goes to the taxidermist’s shop to look for his son was unintentionally amusing. I.e., it was funny how the employees of the business made sure to remove the stuffed animals from the area as Stewart was struggling with them; they obviously didn’t want their expensive “merchandise” damaged - LOL. Also, this scene had shades of the later Psycho - i.e., Norman Bates was a amateur taxidermist in this film.
Some notes re: the 1934 version - no big SPOILERS here, since I know not everyone has seen this yet:
-I had seen both versions of the film for the first time back in the mid-200X’s (on DVD), and when I thought back on the '56 version, I could swear that Doris Day was singing Que Sera, Sera to her young daughter, not young son. However, in this case I was obviously confusing the first film with the second; in the '34 version, the couple’s young pre-teen daughter is kidnapped.
-Peter Lorre played a great, sleazy villain in this film - he was obviously known for these types of roles.
-I liked how the mother took an active role in her daughter’s rescue at the end of the film, and appreciated how this tied into a scene in the beginning of the film. Well-done continuity here.